Subminiature electric motor



June 25, 1963 N- L. CASE ETAL 3,095,515

SUBMINIATURE' ELECTRIC MOTOR Filed Nov. 6, 1961 5 Sheets-Sheet 1 mmaa= F/ 3 N05: A. 64.56

ATTORNIVJ June 25, 1963 N. L. CASE ETAL SUBMINIATURE ELECTRIC MOTOR 3 Sheets-Sheet 2 Filed Nov. 6, 961

FIG, 4

INVENTORS. Wu 1. l: E. IPFXFOIPD N051. 45: BY 2 ATTORAMKS June 25, 1963 N. L. CASE ETAL 3, ,5

I SUBMINIATURE ELECTRIC MOTOR Filed Nov- 6, 1961 3 Sheets-Sheet 3 FIG. 7

INVENTORS. W/u/s 5. REA'FORP ,vozz 1. ans:

United States This invention relates to electric motors, and more particularly to a very small motor commonly called a subminiature motor.

When an electric motor is brought down to extremely small size, the conventional construction techniques used for motors, even of small size, are no longer practical. The general object of the present invention is to improve subminiature electric motors, and to provide such a motor with a different construction and assembly, such thatthe motor may be made at very low cost by mass production methods.

A further object is to provide such a motor which generates an unusually large amount of power relative to the size of the motor. Still another object is to provide such a motor which may be manufactured without critical tolerances or precision dimensioning of its parts. A further object is to provide a motor using-permanent magnets which are simple slabs of rectangular shape, obtainable at minimum cost. Another object is to simplify the provision of external electrical connections to the motor.

The field and brush structure are not claimed herein,

being claimed in our divisional application Ser. No. 239,126, filed November 20, 1962.

To accomplish the foregoing general objects, and other more specific objects which will hereinafter appear, our invention resides in the motor elements and their relation one to another, as are hereinafter more particularly described in the following specification. The specification is accompanied by drawings in which:

FIG. 1 is a perspective view showing a subminiature electric motor embodying features of our invention;

FIG. 2 is a perspective view of the armature, commutator, and shaft assembly;

FIG. 3 isqa section taken through the motor approximately in the plane of the line 33 of FIG. 1, and drawn to enlarged scale;

FIG. 4 is a fragmentary section through one of the brushes, and is taken approximately in the plane of the line 4--4.of FIG. 3, this being drawn to still larger scale;

FIG. 5 is a transverse section through the motor taken approximately in the plane of the line 55 of FIG. 3;

FIG. 6 is an exploded view drawn in perspective and showing the parts of the motor; and

FIG. 7 is a perspective view showing a toy autoin which the motor is mounted for propulsion of the same.

Referring to the drawing, and more particularly to FIG. 1, the motor body there shown has a body dimension of only inch by inch by 4 inch. The overall maximum length including the shaft extensions at each end, is only one inch.

Referring now to FIG. 7, themotor 12 is disposed in a toy vehicle 14 to propel the same. The motor is disposed horizontally, with its shaft extending in fore and aft direction. It drives the rear wheel 16 through gearing not shown, except for the final gear 18. This vehicle is used as part of a speedway toy, the vehicle being guided at its forward end. by means of a guide finger 20 running in a guide groove. Power is supplied through metal power supply stripsv slidably engaged by contacts 22 and 24 which are, pivoted at their ends, and insulated from one another. The road. contact 24 leads to an upright spring, contact 26 which bears against one side of the motor, and road contact 22v leads to a similar atent 3,095,515 Patented June 25, 1963 upright spring contact bearing against the opposite sideof the motor. These upright contacts supply current to the motor in a manner described later.

The speedway may be supplied with current at avoltage of say 12 volts, and the motor, despite its small size, will accept this or even higher voltage, with consequent high power output relative to its exceedingly small dimensions. In consequence, the vehicle may be driven athigh speed, appropriatefor a racing car.

Referring now to FIG. 6 of the drawing, the armature and shaft assembly comprises ferrous laminations 30 which provide armature poles, there being three in the present case. A body of plastics material is molded di-' reotly around the laminations 30", and referring to FIG. 5, this body provides insulation lining in the slots of the armature, as is shown at 32. Referring to FIG. 3, this insulation material is also carried around the ends of the laminations, as shown at 34. It further provides shaft ends 36 and 38 which are preferably stepped in diameter, as shown at 40 and 42, to act as thrust bosses. Reverting to FIG. 6, the insulation body also provides a commutator segment locating cylinder 44 with ridges 46. It further provides end extensions of the armature poles, shown at 48 and 50; In the present case the armature has three poles, and there are three extensions at each end, but each extension is preferably centrally slotted at shown at 52.

The commutator is made up of somewhat L-shaped segments, shown at the right of the armature body in FIG. 6. There are three commutator segments 54 of arcuate cross section, and each has a soldering post 56 bent radially outward therefrom. The segments 54 are placed about the cylinder 44 between the ridges 46, with the posts 56 extending along the insulation end surface of the armature body.

An insulation piece, which may for convenience be called a spider, is provided to hold the commutator segments. The spider comprises a collar 58 which may he slid over the segments 54, and radial parts 60 which then lie outside the metal soldering posts 56 and provide an insulation covering for the same. At this time the posts 56 extend through the slots 52. of the armature extensions 50 previously referred to. The radius of the posts then is. substantially greater than that ofthe armature, by an amount roughly indicated by the reduced end portions 62 of the posts 56.

The windings indicated at 64 in FIG. 2 are then applied. No attempt has been made to show the windings in FIG. 6. The windings fill the armature slots, substantially as shown in FIG. 5, and there is room for a substantial number of turns. The winding also fills the spaces at the ends of the armature beneath the extensions 48 and 50, and the said extensions are provided to protect and to help hold the windings in position.

It is important to note that the wire is wound about the soldering posts. 56 and also the insulation radial posts 60 of the spider, thusadditionally holding all of these parts in assembled relation. The ends of the windings are soldered to the ends 62 of the soldering posts, which is readily done because these parts then project outward and are fully exposed. Finally the thinned end portions 62 of the soldering posts are bent to a positionsubstantially parallel to the shaft, as shown at'62 in FIGS. 2. and 3, thus bringing the same within the radius of the armature. The bent part of the post is protectively housed in the, slots 52. of the extensions 50 previously referred to.

To supply current to the armature there are two diametrically opposed. brush assemblies. Each brush assembly includes a brush 66 (FIG. 4), a brush spring'68, which. fits around the brush, and a tubular metal brush holder 70 diamensioned to receive the brush and spring. The outer end 72 of the spring extends diametrically and 3 bears against the outer end of the brush, and the inner end of the spring is expanded to larger diameter to bear against the inner end of the tubular holder 70 as shown at 74. Thus the spring acts as a pull spring, rather than a push spring, and urges the brush 66 against the commutator segments 54.

The brush holder is itself held by insulation means shown at 120 and 126 in FIG. 3, including a ridge 80 which enters an annular slot 82 of brush holder 70 to lock it against axial movement. The outer end of the metal brush holder 70 is exposed at the outside of the motor to receive the indented end 84 (FIG. 4) of a spring contact 26 which supplies power to the motor. This is the contact previously referred to at 26 in FIG. 7, and it will be understood that there is a similar contact at the opposite side of the motor for connection to the opposite brush holder. Current flows through the brush holder 70 and spring 68 to the brush 66, and thence to the commutator segments 54.

Reverting to FIG. 6, the field is provided by a pair of permanent magnets 90 and 92 disposed on opposite sides of the armature. These may be simple flat rectangular slabs of a highly magnetic material. An alloy such as Alnico may be employed, but in the present case the magnets are ceramic magnets. The direction of magnetism is between the flat faces, that is, in the direction of the shortest dimension of the slab. Thus, if the top of magnet 90 is south, the bottom face adjacent the armature is north, and the magnet 92 then is positioned with its south pole on top or adjacent the armature, and with its north pole at the bottom. They could both be reversed. I

The magnetic circuit is completed by a ferrous yoke 94 and an end plate 96, which parts also act as theoutside frame and easing of the motor. However, the assembly is completed and is greatly facilitated by the use of molded retainers 98 and 100, which are molded in desired shape out of a suitable plastics material. The part 98 is received between the arms 102 and 104 of yoke 94, and it has small shelf-like ledges 106 near the top which receive one end of upper magnet 90. There are similar ledges 108 near the bottom which receive one end of the lower magnet 92. The outer faces of the magnets are attracted to and bear directly against the ferrous metal of the yoke. The end wall 110 of retainer 98 has a bearing 112 (FIG. 3) for the armature shaft 36. The iron yoke 94 (FIG. 3) has a hole dimensioned to receive the outside of the bearing 112. The hole is also shown at 112' in FIG. 6.

Reverting to FIG. 6, the other plastics retainer 100 similarly has upper ledges 114 to support one end of magnet 90, and lower ledges 116 to support one end of magnet 92. The retainer is deeply channelled at 118 to receive the tubular metal brush holders 70, and the bottom wall of the chanel has two transverse ridges (not visible in FIG. 6) corresponding to the ridge 80 shown in FIG. 4 to hold the brush holders against axial movement. There is a peripheral projection 120 (FIG. 6) around the channel 118 at the top and bottom of the retainer, which is received in and which lines mating slots 122 at the ends of the yoke arms 102 and 104. This insulation lining is also shown at 120 in FIGS. 3 and 4.

The retainer 100 (FIG. 6) is completed by a bearing 122 for the armature shaft, and this is received in a mating hole 124 in ferrous end plate 96. The latter is lined with a piece of sheet insulation 126, and this may be cut away as shown at 128, to fit around a wall 129 which carries the bearing 122. The insulation strip 126 preferably has projections 130 at the top and bottom to complete the insulation around the outer ends of the brush holders. These projections 130 complement the insulation rim 120 previously referred to.

The ferrous end plate 96 is notched at 132, and the ends of the yoke are correspondingly shaped to provide tongues which are matingly received in the notches 132. The assembly then may be completed by staking, that is, the interfitting tongues may be struck and expanded 4 somewhat to lock the parts in the assembled relation shown in FIG. 1.

'In the particular motor shown, the winding employs 350 turns of #40 wire for each pole. The wire is plastic coated copper wire. The three windings are delta connected. This is for use at 12 volts, but the motor is useable over a wide range of from 4 to 18 volts.

The armature laminations 30 are stamped out of conventional ferrous metal used for this purpose, and commonly referred to as electrical steel sheet. However, the anmature core also may be made of sintered iron or an iron slug. The plastics material used is preferably nylon. The yoke 94 and end plate 96 for the magnetic circuit may be stamped out of electrical steel sheet. The commutator segments may be made of copper, preferably hardened for better wear. The brush is made of graphite, and the brush holder may be made of brass tubing. The magnet retainers, the armature body and shaft, and the spider, are molded out of nylon. The insulation sheet 126 may be stamped out of sheet fiber or other sheet insulation material.

It is believed that the construction and method of assembly of our improved subminiature electric motor, as well as the advantages of the same, will be apparent from the foregoing detailed description. The insulation parts are molded in final form in a production molding operation. The metal parts are stampings. The assembly is quick and easy. The only soldering needed is to the ends of the soldering posts, which then are fully exposed to facilitate the soldering operation. The magnets may be simple rectangular slabs, obtainable at minimum cost. The armature accepts a large amount of winding relative to its size, and the motor therefore may be wound to operate at a relatively high voltage, with corresponding substantial power output, considering the small size of the motor. The motor operates successfully over a wide range of voltage.

It will be understood that while we have shown and described the invention in a preferred form, changes may be made in the structure shown, without departing from the scope of the invention as sought to be defined in the following claims.

We claim:

1. A miniature motor including an armature assembly, said assembly comprising a ferrous armature core having poles and having no shaft hole, and a body of plastics material molded around the poles, said body of plastics material providing solid insulation shaft ends for supporting the armature and also providing an insulation lining in the slots of the armature and around the ends, and also providing a commutator segment-locating cylinder, said insulation shaft ends being the sole shaft of the armature.

2. A motor as defined in claim 1 and further comprising metal commutator segments extending axially and disposed about said cylinder, each segment having a soldering post disposed radially outward from the segment and extending along the aforesaid insulation material at one end of the armature core, an insulation collar around the inner ends of the segments, windings around the armature poles and soldering posts, the ends of said windings being electrically connected to the outer ends of the soldering posts.

3. A miniature motor including an armature and shaft assembly, said assembly comprising a ferrous armature core having poles and having no shaft hole, a single body of plastics material molded around the poles, said body of plastics material providing an insulation lining in the slots of the armature and around the ends, and providing solid insulation shaft ends at both ends of the armature, and also providing an insulation commutator segmentlocating cylinder and ridges, and further providing insulation end extensions of the poles to help retain and protect the armature windings, and metal commutator segments received between and being separated by said ridges of said cylinder, said insulation shaft ends being the sole shaft of the armature.

4. A miniature motor including a housing with bearings, and an armature and shaft assembly, said assembly comprising a ferrous armature core built up of imperforate laminations and having poles, and a single body of plastics material molded around the poles, said body of plastics material providing an insulation lining in the slots of the armature and around the ends, and also providing solid insulation shaft ends at both ends of the armature, said shaft ends being received in said bearings and constituting the sole shaft of the armature.

5. A miniature electric motor including an armature and shaft assembly, said assembly comprising ferrous laminations providing armature poles, and a single body of plastics material molded around the laminations, said body of plastics material providing an insulation lining in the slots of the armature and around the end laminations, and providing solid insulation stepped shaft ends of small diameter at both ends of the armature with the steps acting as thrust bosses, and also providing an insu lation commutator segment-locating cylinder, and further providing insulation extensions at the outer ends of the poles which extend in axial direction to help retain and protect the armature windings, said insulation shaft ends being the sole shaft of the armature.

6. A miniature motor comprising a ferrous armature core having poles and having no shaft hole, and a plastics insulation body molded therearound and providing an insulation lining in the slots of the armature and aroundthe end laminations, and also providing an insulation commutator segment-locating cylinder, and also providing solid insulation shaft ends, L-shaped metal commutator segments extending axially and disposed about the outside of said cylinder, each segment having a soldering post disposed radially outward from the segment adjacent the aforesaid insulation material molded around an end lamination, and windings around the armature poles and soldering posts whereby the windings help hold the parts in assembled relation, the ends of said windings being electrically connected to the outer ends of the soldering posts, and said insulation shaft ends being the sole shaft of the armature.

7. A motor comprising an armature core, and a plastics insulation body molded therearound and providing an insulation lining in the slots of the armature and around the end laminations, and also providing solid insulation shaft ends for supporting the armature, and also providing an insulation commutator segment-locating cylinder, and further providing insulation end extensions of the poles, said insulation shaft ends being the sole shaft of the armature, L-shaped metal commutator segments extending axially and disposed about said insulation cylinder, each segment having a soldering post disposed radially outward from the segment and extending along the aforesaid insulation material at one end of the armature core, an insulation spider including a collar around the inner ends of the segments and radial legs lying outside the soldering posts, windings around the armature poles and soldering posts and spider legs and beneath said end extensions, the ends of said windings being electrically connected to the ends of the soldering posts, said end extensions of the poles at the soldering posts being slotted in axial direction to provide deep notches in which the outer ends of the soldering posts are received, said soldering posts having an effective length from the axis of the armature substantially greater than the radius of the armature, said spider legs being substantially shorter than the soldering posts and terminatin at a radius less than that of the armature, the outer end of each soldering post being bent around the end of its adjacent spider leg and being received within the corresponding slot of the end extension.

8. A motor including an armature assembly, said assembly comprising ferrous armature poles, and a body of plastics material molded around the poles, said body of plastics material providing insulation shaft ends for supporting the armature, and also providing an insulation lining in the slots of the armature and around the ends, and also providing a commutator segment-locating cylinder, metal commutator segments extending axially and disposed about said cylinder, each segment having a soldering post disposed radially outward from the segment and extending along the aforesaid insulation material at one end of the armature core, an insulation spider including a collar around the inner ends of the segments and including radial parts lying alongside the outer faces of the soldering posts, windings around the armature poles and soldering posts and radial parts of the spider, the ends of said windings being electrically connected to the outer ends of the soldering posts, said insulation shaft ends being the sole shaft of the armature.

9. A motor including an armature and shaft assembly, said assembly comprising ferrous armature poles, and a single body of plastics material molded around the poles, said :body of plastics material providing an insulation lining in the slots of the armature and around the ends, and providing insulation shaft ends at both ends of the armature, and also providing an insulation commutator segment-locating cylinder and ridges, and further providing insulation end extensions of the poles to help retain and protect the armature windings, metal commutator segments extending axially and disposed about said cylinder between said ridges, each segment having a soldering post disposed radially outward from the segment and extending along the aforesaid insulation material at one end of the armature core, an insualtion spider including a collar around the inner ends of the segments and including radial parts lying alongside the outer faces of the soldering posts, windings around the armature poles and soldering posts and radial parts of the spider, the ends of said windings being electrically connected to the outer ends of the soldering posts, said insulation shaft ends being the sole shaft of the armature.

10. A subminiature electric motor including an armature and shaft assembly, said assembly comprising ferrous l-aminations providing armature poles, and a single body of plastics material molded around the laminations, said body of plastics material providing an insulation lining in the slots of the armature and around the end laminations, and providing insulation stepped shaft ends at both ends of the armature with the steps acting as thrust bosses, and also providing an insulation commutator segment-locating cylinder, and further providing insulation end extensions of the poles to help retain and protect the armature windings, metal commutator segments extending axially and disposed about said cylinder, each segment having a soldering post disposed radially outward from the segment and extending along the aforesaid insulation material at one end of the armature core, an insulation spider including a collar around the inner ends of the segments and including radial parts lying alongside the outer faces of the soldering posts, windings around the armature poles and soldering posts and radial parts of the spider, the ends of said windings being electrically connected to the outer ends of the soldering posts, the end extensions of the poles at the soldering posts being slotted in axial direction to provide deep notc es in which the outer ends of the soldering posts are received, said insulartion stepped shaft ends being the sole shaft of the armature.

11. A motor comprising an armature core and a plastics insulation body molded therearound and providing an insulation lining in the slots of the armature and around the end laminations, and also providing an insulation commutator segment-locating cylinder, L-shaped metal commutator segments extending axially and disposed about said cylinder, each segment having a soldering post disposed radially outward from the segment and extending along the aforesaid insulation material at one end of the armature core, an insulation spider including a 7 collar around the inner ends of the segments and radial parts lying outside the soldering posts, windings around the armature poles and soldering posts and radial parts of the spider, the ends of said windings being electrically connected to the outer ends of the soldering posts.

12. A subminiature electric motor comprising armature laminations and a plastics insu lation body molded therearound and providing an insulation lining in the slots of the armature and around the end laminations, and also providing an insulation commutator segment-locating cylinder and ridges, L-shaped metal commuator segments extending axially and disposed about said cylinder between said ridges, each segment having a soldering post disposed radially outward from the segment and extending along the aforesaid insulation material at one end of the armature core, an insulation spider including a collar around the inner ends of the segments and radial parts lying outside the soldering posts, windings around the armature poles and soldering posts and radial parts of the spider whereby the windings help hold the parts in assembled relation, the ends of said windings being electrically connected to the outer ends of the soldering posts.

13. A motor comprising an armature core, and a plastics insulation body molded therearound and providing an insulation lining in the slots of the armature and around the end lamina Lions, and also providing an insulation commutator segment-locating cylinder, and further pnoviding insulation end extensions of the poles, L- shaped metal commutator segments extending axially and disposed about said insulation cylinder, each segment having a soldering post disposed radially outward from the segment and extending along the aforesaid insulation ma.- terial at one end of the armature core, an insulation spider including a collar around the inner ends of the segments and radial parts lying outside the soldering posts, windings around the armature poles and soldering posts and nadial parts of the spider and beneath said end extensions, the ends of said windings being electrically connected to the ends of the soldering posts, the end extensions of the poles at the soldering posts being slotted in axial direction to provide notches in which the outer ends of the soldering posts are received, said legs of the spider being shorter than the soldering posts.

14. A motor comprising an armature core, and a plastics insulation body molded there-around and providing an insulation lining in the slots of the armature and around the end laminations, and also providing an insulation commutator segment-locating cylinder, and further providing insulation end extension of the poles, L-slraped metal commutator segments extending axially and disposed about said insulation eylinder, each segment having a soldering post disposed radially outward from the segment and extending along the aforesaid insti lation material at one end of the armature core, an insulation spider including a collar around the inner ends of the segments and radial legs lying outside the soldering posts, windings around the armature poles and soldering posts and spider legs and beneath said end extensions, the ends of said windings being electrically connected to the ends of the soldering posts, said end extensions of the poles at the soldering posts being slotted in axial direction to provide deep notches in which the outer ends of the soldering posts are received, said soldering posts having an effective length from the axis of the armature substantially greater than the radius of the armature, said spider legs being substantially shorter than the soldering posts and terminating at a radius less than that of the armature, the outer end of each soldering post being bent around the end of its adjacent spider leg and being received within the corresponding slot or the end extension.

References Cited in the file of this patent UNITED STATES PATENTS 1,464,184 Mansbendel Aug. 7, 1923 1,939,615 Apple Dec. 12, 1933 2,322,020 Hemphill June 15, 1943 2,465,446 Gorfin et al. Mar. 29, 1949 2,603,161 Lloyd July 15, 1952 2,831,991 Perkins Apr. 22, 1958 2,894,156 Kent July 7, 1959 2,939,024 Mabuchi May 31, 1960 2,944,169 Schmidt July 5, 1960 2,978,598 KEIJtO Apr. 4, 1961 2,999,956 Faulhaber Sept. 12, 1961 FOREIGN PATENTS 1,210,349 France Sept. 28, 1959 

1. A MINIATURE MOTOR INCLUDING AN ARMATURE ASSEMBLY, SAID ASSEMBLY COMPRISING A FERROUS ARMATURE CORE HAVING POLES AND HAVING NO SHAFT HOLE, AND A BODY OF PLASTICS MATERIAL MOLDED AROUND THE POLES, SAID BODY OF PLASTICS MATERIAL PROVIDING SOLID INSULATION SHAFT ENDS FOR SUPPORTING THE ARMATURE AND ALSO PROVIDING AN INSULATION 